"Thesatellites are in their intended orbit and everything went as planned," NASA launch director Omar Baez said justafter liftoff.

With their uniqueflying formation--one STEREO vehicle will eventually lead the Earth whilethe other lags behind--the satellites will generate the first near real-time, 3-Dimages of the Sun. STEREO's solar quarries are coronalmass ejections (CMEs), immense eruptions from the Sun that spew high-energy particles which canpose a radiationhazard for astronauts and satellites,as well as interfere with power and communications systems on Earth.

With NASA'splan to send astronauts on long-duration missions to the Moon--let alone a future multiple-yeartrip of a Mars-bound flight--more dependable CME and space weather predictionwill prove vital, researchers said.

"They can receivea year's worth of radiation in one of these storms," STEREO project managerNicholas Chrissotimos, of NASA's Goddard Space FlightCenter, said of astronauts working outside a spacecraft or lunar shelter. "Ifwe can predict when these storms occur, we can at least safe the astronautsduring these timeframes so they are not exposed to this environment."

Engineersat the Johns Hopkins University's Applied Physics Laboratory built the STEREOspacecraft for NASA, and will oversee the $550 million mission from a controlcenter in Laurel, Maryland.

Thursday'slaunch came after a series of delays, including last-minute range safety andbooster concerns that were ultimately cleared, but only after pushing the spaceshot to the end of its 15-minute launch window.

"We are atthe dawn of a new age of solar observation," said theU.S. Naval Research Laboratory's Russ Howard, principal investigator for one ofSTEREO's instrument suites. "We are going to be viewing things in a newdimension."

Eyes onthe Sun

The twin STEREO--shortfor Solar Terrestrial Relations Observatory--spacecraft are aptly named. Onvehicle, billed as Ahead, is destined to lead the Earth in its orbit while the satellite'sBehind counterpart will lag aft of the planet.

In order toreach their final positions, STEREO's Ahead vehicle will slingshot around theMoon to move into an Earth-leading orbit. The Behind vehicle, meanwhile, willmake another swing past the Moon to reach its Earth-trailing position. Both STEREOspacecraft are expected to slowly widen the gap between each other over time,mission managers said.

Each STEREOsatellite packs 16 Sun-watching instruments into a frame about the size of agolf cart and weighs about 1,364 pounds (620 kilograms). Researchers hope tobring the Sun-watching duo online after a 90-day checkout period to add to currentassets like Solar and HeliosphericObservatory (SOHO) and other missions such as Windand AdvancedComposition Explorer (ACE).

"Just likeyou cannot measure ocean current with just a few buoys, you really cannot tryto understand this space environment with just a few observatories," NASA'sSTEREO program scientist Madhulika Guhathakurta saidbefore today's launch.